An automatic sprinkler system is one of the most widely used devices for fire protection. These systems have sprinklers that are activated once the ambient temperature in an environment, such as a room or a building, exceeds a predetermined value. Once activated, the sprinklers distribute fire-extinguishing fluid, preferably water, in the room or building. A sprinkler system, depending on its specified configuration is considered effective if it controls or suppresses a fire. Failures of such systems may occur when the system has been rendered inoperative during building alteration or disuse, or the occupancy hazard has been increased beyond initial system capability.
The sprinkler system can be provided with a suitable fire fighting fluid or a water supply (e.g., a reservoir or from a municipal water supply). Such supply may be separate from that used by a fire department. Regardless of the type of supply, the sprinkler system is provided with a main that enters the building to supply a riser. Connected at the riser are valves, meters, and, preferably, an alarm to sound when water flow within the system is above or below a predetermined minimum value. At the top of a vertical riser, a horizontally disposed array of pipes extends throughout the fire compartment in the building. Other risers may feed distribution networks to systems in adjacent fire compartments. Compartmentalization can divide a large building horizontally, on a single floor, and vertically, floor to floor. Thus, several sprinkler systems may serve one building.
In a piping distribution network, branch lines carry the sprinklers. A sprinkler may extend in a pendant, upright or horizontal fashion from a branch line, placing the sprinkler relatively close to the ceiling. For a horizontal sprinkler, the sprinkler may be located, for example, between four and twelve inches below the ceiling.
Various standards exist for the design and installation of a fire protection system. For example, National Fire Protection Association (“NFPA”) publishes the following standards for the design and installation of fire protection systems: (i) “NFPA 13: Installation of Sprinkler Systems” (2002) (hereinafter “NFPA 13 (2002)”); (ii) “NFPA 13D: Installation of Sprinkler Systems In One- and Two-Family Dwellings and Manufactured Homes” (2002) (hereinafter “NFPA 13D (2002)”); and (iii) “NFPA 13R: Standard For the Installation of Sprinkler Systems in Residential Occupants Up To and Including Four Stories In Height” (2002) (hereinafter “NFPA 13R (2002)”) and collectively referred to herein as “NFPA 13, 13D, and 13R (2002).” NFPA 13, 13D, and 13R (2002) and any of their updated editions, such as NFPA 13 (2007), provide various design considerations and installation parameters for a fire protection system. NFPA 13, 13D, and 13R (2002) recognize the use of residential sprinklers by requiring that such a sprinkler in a residential fire protection system be installed based on certain criteria for residential occupancies, which can include commercial dwelling units (e.g., rental apartments, lodging and rooming houses, board and care facilities, hospitals, motels or hotels).
In order, however, for a residential sprinkler to be approved for installation under NFPA Standards, such as NFPA 13, 13D and 13R (2002), the sprinkler typically must pass various tests promulgated by, for example, Underwriters Laboratory Incorporated (“UL”) in its standard entitled “UL 1626: Residential Fire Sprinklers For Fire-Protection Service” (October 2003) (hereinafter “UL Standard 1626 (October 2003)” and which is incorporated by reference in its entirety), in order to be listed for use as a residential sprinkler. Specifically, UL Standard 1626 (October 2003) requires a sprinkler, as described in Table 6.1 of Section 6, to deliver a minimum flow rate (gallons per minute or “GPM”) for a specified coverage area (square feet or “ft2”) to provide for a desired average density of 0.05 GPM/ft2. The minimum flow rate tabulated in Table 6.1 can be used to calculate a predicted minimum fluid pressure needed to operate a sprinkler by virtue of a rated K-factor of the sprinkler. A rated K-factor of a sprinkler provides a coefficient of discharge of the flow passage of the sprinkler, is defined as follow:
      K    -    factor    =      Q          p      
where Q is the flow rate in GPM and p is the pressure in pounds per square inch gauge.
In order for a sprinkler to pass actual fluid distribution tests, as described in Sections 26 and 27 of UL Standard 1626 (October 2003), the actual minimum pressure of the sprinkler, may not be the same as the predicted minimum pressure, which can be calculated using the given minimum flow rate of Table 6.1 in UL Standard 1626 (October 2003) and the rated K-factor of the sprinkler. Further, the actual minimum fluid flow rate to pass these distribution tests of UL Standard 1626 (October 2003) for a specified coverage area may even be higher than the tabulated minimum flow rate given in Table 6.1 of UL Standard 1626 (October 2003). Consequently, any attempt to provide for a listed sprinkler (i.e., an operational sprinkler suitable for the protection of a dwelling unit) cannot be predicted by applications of a known formula to known residential sprinklers.
Known residential sidewall fire sprinklers have been tested to meet these performance qualifications required by UL Standard 1626 (October 2003). When these known sprinklers are designed to be installed in an actual system according to NFPA 13, 13D, and 13R (2002) for a large protection area of 324 square feet or greater, however, these existing residential fire sprinklers require a fluid pressure, based on its discharge coefficient or K-factor, that places a greater demand on the fluid pressure source than that predicted by the application of the tabulated minimum flow rate of UL Standard 1626 (October 2003) and the rated K-factor. Moreover, for some sprinklers, the range of uniform pressure and flows to satisfy the standards vary widely depending on spacing of the sprinkler from the ceiling, i.e., the ceiling-to-deflector spacing.
It would be beneficial to provide for a residential sprinkler to achieve a more uniform pressure demand independent of distance from the ceiling, while meeting the performance requirements of a listing authority, such as, for example, the tests set forth in UL Standard 1626 (October 2003), including vertical and horizontal fluid distribution tests. A uniform pressure demand for a horizontal residential fire sprinkler over a range of ceiling-to-deflector spacings would allow a fire protection system designer to have greater leeway in residential applications that are installed in accordance with the requirements of NFPA 13, 13D, and 13R (2002). Further, the more uniform pressure demand of such sprinkler would preferably provide a minimum design pressure that will allow such designer to tailor the location of sprinklers from the ceiling demanded by the design protection area for a system installed in accordance with NFPA 13, 13D, and 13R (2002).